What is the working principle of a gear grinding machine

The working principle of a gear grinding machine can be divided into two categories: forming method and generating method.

1. Molding method

In a form-gear grinding machine, the grinding wheel is shaped into its tooth profile in the axial section by a form-gear dresser, and the grinding wheel head can be fed vertically. The gear being ground is supported by an indexing head and a tailstock, and the worktable performs a longitudinal reciprocating motion to grind the tooth surface. Indexing is performed after each tooth is ground. On a machine tool for grinding helical gears, the grinding wheel can rotate at an angle according to the helix angle of the workpiece, allowing the workpiece to rotate additionally during the reciprocating motion. If the machine tool's grinding wheel head can allow the grinding wheel to enter the internal gear workpiece, internal gears can be ground. Form-gear grinding machines have a simple structure, high efficiency, and accuracy up to grade 5. They are suitable for batch production and are particularly suitable for gears with a small number of teeth (e.g., less than 10).

2. Spreading method

Gear grinding machines that use the generating method can be divided into four types based on the shape of the grinding wheel.

① Disc-shaped grinding wheel gear grinding machine: The narrow sides of two rotating disc-shaped grinding wheels correspond to the two tooth surfaces of a gear rack. The workpiece undergoes generating motion via a rolling disc and a steel belt, while the worktable reciprocates along the workpiece's axial direction to grind the entire tooth width. After each tooth is ground, the indexing headstock divides the tooth through the indexing plate. This machine tool can also grind helical gears using additional devices. If a grinding wheel is inserted into the internal gear, internal gears can be ground. This machine tool is generally horizontally oriented, but a vertical orientation is used when machining diameters greater than 1 meter. Accuracy can reach grade 4, making it suitable for grinding high-precision gears.

② Conical Grinding Wheel: The axial profile of the grinding wheel is dressed to form one tooth profile of a rack, and it reciprocates linearly along the tooth direction. The workpiece completes the generating and indexing movements through a worm gear, lead screw, and changing gears. However, some machines use a rolling disc and steel belt for generating movements and a worm gear pair or indexing plate for indexing movements. The grinding wheel head can grind helical gears when it rotates through a certain angle according to the helix angle of the workpiece. This type of machine tool is easy to adjust, has good versatility, is suitable for single-piece and batch production, and is widely used.

③ Worm Gear Grinding Machine: The principle is similar to that of a gear hobbing machine. The grinding wheel is a large-diameter, single-start worm shape. For each revolution of the grinding wheel, the workpiece rotates one tooth. The transmission ratio is accurate. Some use mechanical transmission, some use synchronous motors for separate drives, and some use grating and servo motors for transmission. During grinding, the workpiece moves axially to grind the entire tooth surface. The grinding wheel is machined with a diamond turning tool or rolled into a worm shape using a roller. The machine tool has a vertical layout, continuous indexing, and high grinding efficiency. It is suitable for batch production of gears with medium module, especially for gears with many teeth, achieving an accuracy of up to grade 4.

④ Large-plane grinding wheel gear grinding machine: The working plane of the grinding wheel is equivalent to one tooth surface of the rack. Generating motion is generated using an involute template (sometimes a steel strip and rolling disc are used). Neither the grinding wheel nor the workpiece undergoes axial reciprocating motion. After grinding one side of the tooth surface, the teeth are divided using an indexing plate, and all tooth surfaces are ground sequentially. Then the workpiece is turned around, and the other side of the tooth surface is ground. The machine tool has a horizontal layout, simple structure, stable performance, and an accuracy of up to grade 3. It is mainly used for grinding gear shapers, gear shaving cutters, and measuring gears for measurement purposes.